Energy response of a room-temperature cadmium telluride (CdTe) photon-counting detector for simultaneous and sequential CT and SPECT

Semiconductor radiation detectors are a promising technology for single photon counting detectors. Unlike scintillator-based indirect radiation detectors, semiconductor detectors directly convert absorbed photons to charge, thereby reducing energy spreading and signal loss that can occur in scintillator-based detectors. Cadmium telluride (CdTe) has attracted research interest due to its higher stopping power compared to other semiconductors such as germanium and silicon as well as its room-temperature operating capability. A CdTe photon-counting, energy-resolving detector system has been developed for x-ray and radionuclide imaging, and is capable of discriminating incident photon energy using multiple voltage thresholds per detector element with fast signal formation. Using this CdTe detector, a reproducible method of generating energy spectra was developed for a given incident radiation source. The energy resolution of the CdTe detector was determined by generating the energy spectra of three radiation sources. The full-width half-maximum (FWHM) energy resolution of the CdTe photon-counting detector was determined. The energy spectrum of a 50-kV x-ray source and a ⁵⁷Co source was simultaneously acquired without degradation in energy resolution. The energy spectrum from the CdTe photon-counting detector provides useful spectral information for imaging tasks that use the same detector. Simultaneous or sequential x-ray computed tomography (CT) and single photon emission tomography (SPECT) may be feasible with this CdTe photon-counting detector.